CN113470896B - Method for integrating extensible stimulation electrode on surface of semi-inflatable micro-balloon - Google Patents

Abstract

The invention discloses a method for integrating extensible stimulating electrodes on the surface of a semi-expansive micro-balloon, which comprises the following steps of firstly, pressing a water-soluble adhesive tape on the extensible stimulating electrodes, and applying uniform pressing force; then inflating or injecting a contrast agent into the micro-balloon to enable the micro-balloon to reach a semi-expansion state, and uniformly brushing adhesive silica gel on the surface of the micro-balloon to serve as an adhesive material between the micro-balloon and an extensible stimulation electrode; then slowly stripping the stimulating electrode from the silicon wafer through a water-soluble adhesive tape, attaching the stimulating electrode to the target position of the microballoon capsule coated with the viscous silica gel, and then placing the whole microballoon capsule in an oven to dry the viscous silica gel; and finally, fully soaking the micro-balloon in hot water to ensure that the water-soluble adhesive tape is completely dissolved and the stimulating electrode point and the annular ground electrode are completely exposed. The method can ensure that the extensible stimulation electrode deforms synchronously along with the expansion or contraction of the microsphere capsule, meets the requirement of higher deformation and stretching of the microsphere capsule, and has important practical value and innovation significance.

Description

A method for integrating stretchable stimulating electrodes on the surface of a semi-expandable microballoon

technical field

The invention belongs to the technical field of biomedical electricity, and in particular relates to a method for integrating an extensible stimulation electrode.

Background technique

With the development of flexible electronic device technology, some studies have reported the integration of flexible devices on the surface of microballoons for cardiac diagnosis and treatment to realize functions such as ECG monitoring, temperature sensing, pressure sensing, and radiofrequency ablation. At present, most of the microballoons are made of polyurethane material with small deformation. The elastic deformation during the inflation and deflation process is small, and the deflated state is mainly shriveled and wrinkled.

In the prior art, in 2012, Dae-Hyeong Kim et al. of Seoul National University, Korea, wrote an article "Electronic sensor and actuator webs for large-area complexgeometry cardiac mapping and therapy" in PNAS, 2012, 109(49): 19910-19915, proposing a balloon Surface-integrated tactile sensor with serpentine wire structure for measuring electrical resistance to verify the degree of contact with tissue; in 2015, Lauren Klinker et al. of MC10 company in the United States wrote "Balloon catheters with integratedstretchable electronics for electrical stimulation," ExtremeMechanics Letters, 2015, 3:45-54. "ablation and blood flow monitoring", proposed a serpentine wire structure electrode with a polyimide substrate integrated on the surface of the balloon, which has functions such as electrical stimulation and radiofrequency ablation; ): 1674-1677 wrote "Flexible Multi-Positional Microsensors for Cryoablation Temperature Monitoring", proposing a Parylene-C substrate flexible temperature sensor with a serpentine wire structure integrated on the surface of a large-sized balloon for cryoablation low temperature detection; 2020 Northwestern University, USA The John A. Rogers team wrote an article "Catheter-integrated softmultilayer electronic arrays for multiplexed sensing and actuation during cardiac surgery" in NatureBiomedical Engineering, 2020, 4(10):997-1009, proposing a polyimide with a serpentine wire structure integrated on the balloon surface The base electrode detects the electrical signal of the endocardium, and ablates part of the myocardial tissue by means of local heating, so as to realize the treatment of arrhythmia and the simultaneous pressure detection. Although the above research has carried out a serpentine structure design for the device wire, in order to improve the overall ductility, the balloon expansion deformation in the inflated state is small, so the ductility of the wire is not required to be high.

Another type of micro-balloon uses a large deformation silicone resin material (such as latex), which has a large amount of elastic deformation during inflation and deflation, and can expand from an initial cylindrical shape to a spherical shape and can return to a cylindrical shape. In 2011, the John A. Rogers team wrote an article "Materials for multifunctional balloon catheters with capabilities in cardiac electrophysiological mapping and ablation therapy" in NATURE MATERIALS, 2011, 10(4): 316-323, and proposed that the surface of the large deformation silicone balloon catheter integrates The flexible device is used for epicardial recording of cardiac electrophysiology, tactile, temperature data and cryoablation. The maximum deformation of the balloon shown is 130%. The flexible device is mainly integrated in the lower half of the balloon near the catheter. The used island-bridge structure deposits silicon dioxide on the back of the island, which is bonded to the elastic substrate by chemical condensation reaction. The bridge, that is, the wire, is in a free-moving state. Provide sufficient extension capacity. However, in this interface integration method, the wires are detached from the substrate with the balloon expansion, and are easily damaged and failed in the process of squeezing and rubbing with the tissue.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the present invention provides a method for integrating extensible stimulating electrodes on the surface of a semi-expandable microballoon. First, a water-soluble adhesive tape is pressed over the extensible stimulating electrodes, and a uniform pressing force is applied; then Inflate or inject contrast agent into the microballoon to make the microballoon reach a semi-expanded state, and evenly brush the surface of the microballoon with viscous silica gel as the adhesive material between the microballoon and the extensible stimulation electrode; The water-soluble tape slowly peels off the stimulating electrode from the silicon wafer, attaches the stimulating electrode to the target position of the micro-balloon coated with adhesive silica gel, and then places the entire micro-balloon in an oven to dry the adhesive silica gel; The balloon is fully immersed in hot water to ensure that the water-soluble tape is completely dissolved, and the stimulating electrode points and the annular ground electrode are fully exposed. The method can ensure that the extensible stimulating electrode deforms synchronously with the expansion or contraction of the micro-balloon, and meets the higher deformation and stretching requirements of the micro-balloon, and has important practical value and innovative significance.

The technical scheme adopted by the present invention to solve its technical problems comprises the following steps:

Step 1: Press the water-soluble tape over the stretchable stimulation electrode encapsulating the metal material of the polyimide film substrate, and apply a uniform pressing force;

Step 2: Inflate the microballoon or inject a contrast agent through the support tube connected to the microballoon to make the microballoon reach a semi-expanded state, and then evenly brush the surface of the microballoon with viscous silica gel;

Step 3: Peel the malleable stimulation electrode from the silicon wafer with water-soluble tape, attach the malleable stimulation electrode to the micro-balloon coated with adhesive silica gel, and place the micro-balloon on the set parameter. Dry the viscous silica gel in an oven;

Step 4: Fully immerse the dried micro-balloons in hot water to ensure that the water-soluble tape is completely dissolved and peeled off, so that the malleable stimulating electrodes are fully exposed.

Further, the extensible stimulation electrode includes 6 stimulation electrode points, 6 annular ground electrodes and extensible wires; the 6 stimulation electrode points are equally divided into two groups, and the circumferential spacing is 120° distributed in the microballoons respectively. The middle position of the metal ends at both ends; the six annular ground electrodes are respectively semi-enclosed around the six stimulating electrode points; the diameter of the stimulating electrode points is 50-200 microns, and the inner diameter of the ring-shaped ground electrodes is 200-300 microns, which can be The width of the extended wire is 5-50 microns.

Further, the extensible stimulating electrode includes a polyimide substrate layer, a metal conductive layer and a polyimide encapsulation layer, and a serpentine extensible wire structure is obtained by a photolithography process; the material of the metal conductive layer is Cr/ Au or Cr/Pt.

Further, the water-soluble adhesive tape is 3M water-soluble adhesive tape, and the size is 6mm*15mm.

Further, the size of the initial state of the micro-balloon is 1.6 mm in diameter and 11 mm in total length, the diameter of the maximum deformation point when the micro-balloon is in a semi-expanded state is 4 mm, and the diameter of the maximum deformation point when the micro-balloon is fully inflated is 8 mm; The material of the balloon is latex or thermoplastic polyurethane.

Further, the viscous silica gel adopts uncured low-modulus polydimethylsiloxane or low-modulus platinum-catalyzed silicone rubber Ecoflex_gel.

Further, when the microcapsules are placed in an oven with set parameters to dry the viscous silica gel, the temperature in the oven is 70-80 degrees Celsius, and the heating time is 1-4 hours.

Further, the six stimulating electrode points are divided into two groups with a circumferential spacing of 120° and an axial spacing of 10-20 mm, and are distributed on the outer surface of the microballoon at a position of 5-10 mm near the top metal end.

Further, the material of the metal conductive layer is silver nanowires, carbon nanotubes or graphene.

Further, the polyimide substrate layer and the polyimide encapsulation layer can be replaced with PDMS or Ecoflex or PU glue material.

The beneficial effects of the present invention are as follows:

The method of the invention integrates the extensible stimulation electrodes on the surface of the micro-balloon by means of pre-stretching when the micro-balloon is in a semi-expanded state, so as to ensure that when the micro-balloon is in a state of maximum expansion, the deformation of the extensible wire is at the same level as the extensible stimulation electrode. The electrodes can withstand within the maximum deformation limit, and the malleable wires can also be simultaneously compressed and deformed when the microballoon is deflated and deflated. In addition, in order to improve the relative position accuracy of the serpentine wire of the extensible stimulation electrode and the bonding reliability of the surface of the microballoon, and avoid the serious deformation of the extensible wire outside the surface, in the integration process, the viscous silica gel material is used as the bonding material, and the water-soluble material is used. The tape slowly transfers the extensible stimulating electrode to the target position on the surface of the microballoon coated with the adhesive silicone material, thus effectively ensuring the reliability of the adhesion between the extensible stimulating electrode and the surface of the microballoon.

Description of drawings

FIG. 1 is a schematic diagram of the integrated state of the semi-expandable microballoon surface integrating the stretchable stimulating electrodes of the present invention.

FIG. 2 is a schematic diagram of the transfer integration process of the semi-expandable microballoon surface integrating the stretchable stimulating electrodes of the present invention.

FIG. 3 is a schematic diagram of the layered structure of the extensible stimulation electrode structure of the present invention.

FIG. 4 is a schematic diagram of the relative positions of the stretchable stimulation electrodes integrated in the initial state of the microballoon according to the present invention.

FIG. 5 is a schematic diagram of the deformation of the stretchable wire and the corresponding state of the microballoon according to the present invention.

FIG. 6 is a schematic diagram of a partially enlarged structure of the extensible stimulation electrode of the present invention.

In the figure: 1-Extensible stimulating electrode, 2-Microballoon, 3-Metal end, 4-Support tube, 5-Polyimide substrate layer, 6-Metal conductive layer, 7-Polyimide encapsulation layer, 8- Balloon catheter, 9- Initial wire on the surface of the semi-expanded micro-balloon, 10- Compression wire on the surface of the micro-balloon after deflation, 11- Extension wire on the surface of the micro-balloon after inflation, 12- Stimulating electrode point, 13- Ring ground electrode , 14-extensible wire.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

The invention provides a method for integrating extensible stimulating electrodes on the surface of a semi-expandable micro-balloon, which can realize a large-expandable application scenario of integrating a stimulating electrode on the surface of a micro-balloon, and at the same time ensure high adhesion and high reliability between the stimulating electrode and the surface of the micro-balloon sex. The method of the invention involves two parts, a microballoon capable of realizing large extension and an extensible stimulating electrode, and the extensible stimulation circuit is accurately transferred to the surface of the microballoon capable of realizing large extension through a water-soluble adhesive tape.

A method for integrating extensible stimulating electrodes on the surface of a semi-expandable microballoon, comprising the following steps:

Step 1: Press the water-soluble tape over the extensible stimulating electrode and apply a uniform pressing force; ensure that the adhesive force between the water-soluble tape and the stimulating electrode interface enables the stimulating electrode to release from the silicon wafer sprayed with the release agent. It is completely peeled off to ensure that there is sufficient adhesion between the water-soluble tape and the interface of the extensible stimulation electrode, so that the extensible stimulation electrode can be completely peeled off from the silicon wafer with the sacrificial layer removed;

Step 2: Inflate the microballoon or inject contrast agent through the support tube connected to the microballoon to make the microballoon reach a semi-expanded state, and then evenly brush the surface of the microballoon with viscous silica gel as the microballoon and malleable. Adhesive material between stimulation electrodes;

Step 3: Slowly peel the extensible stimulating electrode from the silicon wafer with water-soluble tape, and then attach the extensible stimulating electrode to the corresponding position of the microballoon coated with adhesive silica gel according to the device design scheme, and then attach the microballoon The capsule is placed in an oven with set parameters to dry the viscous silica gel;

Step 4: Fully soak the microcapsule in hot water to ensure that the water-soluble tape is completely dissolved, and the stimulating electrode point and the ring ground electrode are completely exposed.

Further, the extensible stimulation electrode includes 6 stimulation electrode points, 6 annular ground electrodes and extensible wires; the 6 stimulation electrode points are equally divided into two groups, and the circumferential spacing is 120° distributed in the microballoons respectively. The middle position of the metal ends at both ends; the six annular ground electrodes are respectively semi-enclosed around the six stimulating electrode points; the diameter of the stimulating electrode points is 50-200 microns, and the inner diameter of the ring-shaped ground electrodes is 200-300 microns, which can be The width of the extended wire is 5-50 microns.

Further, the extensible stimulating electrode comprises a polyimide substrate layer, a metal conductive layer and a polyimide encapsulation layer, and a serpentine extensible wire structure is obtained by a photolithography process; the material of the metal conductive layer is chromium or gold.

Further, the water-soluble adhesive tape is 3M water-soluble adhesive tape, and the size is 6mm*15mm.

Further, the size of the initial state of the micro-balloon is 1.6 mm in diameter and 11 mm in total length, the diameter of the maximum deformation point when the micro-balloon is in a semi-expanded state is 4 mm, and the diameter of the maximum deformation point when the micro-balloon is fully inflated is 8 mm; The material of the balloon is an elastic material with excellent ductility such as latex and thermoplastic polyurethane (TPU).

Further, the viscous silica gel adopts uncured low-modulus polydimethylsiloxane (PDMS) or low-modulus platinum-catalyzed silicone rubber Ecoflex_gel.

Further, when the microcapsules are placed in an oven with set parameters to dry the viscous silica gel, the temperature in the oven is 70-80 degrees Celsius, and the heating time is 1-4 hours.

Further, the six extensible stimulating electrodes are divided into two groups with a circumferential spacing of 120° and an axial spacing of 10-20 mm, and are distributed on the outer surface of the microballoon at a position of 5-10 mm near the top metal end.

Further, the material of the metal conductive layer is silver nanowires, carbon nanotubes or graphene.

Further, the polyimide substrate layer and the polyimide encapsulation layer can be replaced with PDMS or Ecoflex or PU glue material.

Specific examples:

In this embodiment, referring to FIG. 1 , the malleable stimulation electrode 1 is integrated into the surface of the microballoon 2 in the semi-expanded state, and the overall size of the malleable stimulation electrode 1 is determined by the size of the semi-expanded state of the microballoon 2 , The initial size of the microballoon is 1.6mm in diameter and 11mm in total length. At the same time, the stimulation electrode point on the integrated extensible stimulation electrode 1 is located in the middle of the metal ends at both ends of the microballoon, and the pads of the extensible stimulation electrode 1 are attached. Attached to the surface of the support tube 4, connected to the electrical stimulator through a flexible cable, and inputting stimulation signals to achieve a highly controllable stimulation process.

Referring to Figure 2, the integration method of this embodiment is mainly divided into the following four steps:

Step 1: Press the water-soluble tape over the flexible and extensible stimulating electrode encapsulated by the polyimide film substrate, and apply a uniform pressing force to ensure that there is sufficient space between the interface of the water-soluble tape and the extensible stimulating electrode. The adhesion of the ductile stimulation electrode can be completely peeled off from the silicon wafer with the sacrificial layer removed;

The 3M water-soluble tape used here is cut into a rectangle of 6mm × 15mm to peel off a single extensible stimulating electrode to avoid mis-sticking other devices on the silicon wafer. The stripping process starts from the end of the pad to avoid breakage of the ductile wires during the stripping process. In addition, the water-soluble tape is bent due to the force during the peeling process, and can be restored to a flat surface by external force, which is convenient for subsequent attachment and integration with the surface of the microballoon.

Step 2: Inflate the microballoon or inject contrast agent through the support tube connected to the microballoon to make the microballoon reach a semi-expanded state, the maximum deformation diameter is 4mm, and then evenly brush the surface of the microballoon with adhesive Silica gel, as the adhesive material between the microcapsules and the malleable stimulation electrodes;

Step 3: Slowly peel the extensible stimulating electrode from the silicon wafer with water-soluble tape, attach the extensible stimulating electrode to the corresponding position of the micro-balloon coated with adhesive silica gel according to the device design scheme, and then attach the entire The balloon device is placed in an oven at 70-80°C and heated for 1-4 hours to dry the viscous silica gel;

Step 4: Fully soak the microcapsule device in hot water and shake it properly to ensure that the water-soluble tape is completely dissolved and dropped, and the stimulating electrode point and the annular ground electrode are completely exposed.

Referring to FIG. 3, it is a schematic diagram of electrode layering including a polyimide substrate layer 5, a metal conductive layer 6 and a polyimide encapsulation layer 7 manufactured by a traditional photolithography process; The polyimide (Durimide7505) photoresist was spin-coated by the melter. After pre-baking, photolithography, development, and rinsing, the polyimide was subjected to incomplete imidization using high-temperature pyrolysis and curing equipment under nitrogen environmental protection. The temperature is 250℃, 60min, and the thickness after curing is about 2.5μm. A metal multilayer film magnetron sputtering control system is used to sputter 20 nm of chromium and 200 nm of gold as conductive materials in sequence, and then a dry etching process is used to obtain a metal conductive layer 6 . The polyimide encapsulation layer 7 has the same technological process as the polyimide substrate layer 5 , but the post-baking temperature is set to 350° C. for 60 minutes to perform complete imidization. The polyimide encapsulation layer 7 has a thickness of about 2.5 μm after curing.

Referring to Fig. 4, it is the corresponding position of the extensible stimulation electrode 1 and the micro-balloon 2 in the initial state. When the extensible stimulation electrode is integrated into the micro-balloon, it should be ensured that the stimulation electrode points are located at the metal ends 3 on both sides of the balloon. The neutral position ensures the stability of the electrical stimulation position.

Referring to FIG. 5 , which is the corresponding deformation state of the stretchable wire when the microballoon is in the initial, semi-expanded, and fully expanded states, the method for integrating stretchable stimulation electrodes on the surface of the semi-expanded microballoon in this embodiment is to combine the stretchable stimulation electrodes. With the help of water-soluble adhesive tape, it is integrated into the surface of the semi-expanded microballoon (4mm at the maximum diameter). At this time, the shape of the stretchable wire is the initial wire 9 on the surface of the semi-expanded microballoon. When the microballoon contracts back to the initial state (1.6 mm in diameter) to obtain the compressed wire 10 on the surface of the deflated microballoon, and when the microballoon is fully inflated (8 mm at the maximum diameter) to obtain the stretched wire 11 on the surface of the inflated microballoon.

Referring to FIG. 6, which is a partial enlarged view of the stimulating electrode point 12, the annular ground electrode 13, and the stretchable wire 14, the diameter of the stimulating electrode point is 50-200 microns, and the inner diameter of the ring-shaped ground electrode is 200-300 microns. The width of the extension wire is 5-50 microns, and the annular ground electrode designed in this embodiment is connected to a standard zero potential during electrical stimulation, thereby constraining the electrical stimulation range within an arc range and improving the spatial accuracy of electrical stimulation. The extensible wire adopts the same-direction layout to improve the deformation ability of the extensible wire in the radial and circumferential directions as much as possible, reducing the maximum principal stress on the metal conductive layer of the extensible stimulating electrode during the stretching process, and improving the device reliability.

In another specific embodiment, the electrode positions are varied to achieve a similar electrical stimulation operation. The 6 electrode points are divided into two groups with a circumferential distance of 120° and an axial distance of 10-20mm, and are distributed on the outer surface of the micro-balloon near the top metal end of 5-10 mm to ensure that the electrodes are stimulated during the expansion of the micro-balloon. The point is displaced accordingly, and is mainly located in the area where the main contact with the trigeminal nerve tissue is made, so as to realize the precise and concentrated electrical stimulation function for a specific area.

In another specific embodiment, materials such as silver nanowires, carbon nanotubes, or graphene are used to replace the metal conductive layer in FIG. The imide substrate layer and the polyimide encapsulation layer are replaced, so that the extensible stimulating electrode has stronger extensibility from the perspective of material intrinsic. The designed conductive layer can be printed with the help of high-resolution electro-fluid jet printing equipment, using silver nanowires, carbon nanotubes or graphene as conductive materials; also with the help of high-resolution printing equipment to complete the silicone substrate layer and the silicone packaging layer. Processing, the printed conductive layer is encapsulated, so that the malleable stimulation electrode integrated on the surface of the semi-expanded microballoon has stronger extensibility.

Claims (10)

1. A method for integrating extensible stimulation electrodes on the surface of a semi-inflatable micro-balloon is characterized by comprising the following steps:

step 1: pressing a water-soluble adhesive tape above an extensible stimulating electrode of a polyimide film substrate packaging metal material, and applying uniform pressing force;

step 2: inflating or injecting contrast agent into the micro-balloon through a supporting tube connected with the micro-balloon to enable the micro-balloon to reach a semi-expansion state, and then uniformly brushing viscous silica gel on the surface of the micro-balloon;

and step 3: peeling the extensible stimulation electrode from the silicon wafer through a water-soluble adhesive tape, attaching the extensible stimulation electrode to the micro-balloon coated with the viscous silica gel, and then placing the micro-balloon in an oven with set parameters to dry the viscous silica gel;

and 4, step 4: and fully soaking the dried micro-balloon in hot water to ensure that the water-soluble adhesive tape is completely dissolved and falls off, so that the extensible stimulation electrode is completely exposed.

2. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon according to claim 1, wherein the extensible stimulation electrode comprises 6 stimulation electrode points, 6 annular ground electrodes and an extensible lead; the 6 stimulation electrode points are evenly divided into two groups, and the circumferential intervals of 120 degrees are respectively distributed in the middle positions of the metal ends at the two ends of the micro-balloon; the 6 annular ground electrodes are respectively semi-surrounded around the 6 stimulating electrode points; the diameter of the stimulating electrode point is 50-200 microns, the inner diameter of the annular ground electrode is 200-300 microns, and the width of the extensible lead is 5-50 microns.

3. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon as claimed in claim 1, wherein the extensible stimulation electrode comprises a polyimide substrate layer, a metal conductive layer and a polyimide packaging layer, and a serpentine extensible lead structure is obtained through a photolithography process; the metal conducting layer is made of Cr/Au or Cr/Pt.

4. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon as claimed in claim 1, wherein the water-soluble adhesive tape is 3M water-soluble adhesive tape with the size of 6mm x 15 mm.

5. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon as claimed in claim 1, wherein the size of the micro-balloon in the initial state is 1.6mm in diameter and 11mm in total length, the diameter of the maximum deformation part of the micro-balloon in the semi-inflatable state is 4mm, and the diameter of the maximum deformation part of the micro-balloon in the fully inflatable state is 8 mm; the material of the micro-balloon is latex or thermoplastic polyurethane.

6. The method for integrating the malleable stimulation electrode on the surface of the semi-inflatable micro-balloon according to claim 1, wherein the viscous silicone rubber is uncured low modulus polydimethylsiloxane or low modulus platinum catalyzed silicone rubber Ecoflex gel.

7. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon according to claim 1, wherein when the micro-balloon is placed in an oven with set parameters and viscous silica gel is dried, the temperature in the oven is 70-80 ℃, and the heating time is 1-4 hours.

8. The method for integrating extensible stimulation electrodes on the surface of the semi-inflatable micro-balloon according to claim 2, wherein the 6 stimulation electrode points are divided into two groups, the distance between the two groups is 120 degrees in the circumferential direction, the distance between the two groups is 10-20 mm in the axial direction, and the stimulation electrode points are distributed on the outer surface of the micro-balloon at positions 5-10 mm close to the top metal end.

9. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon as claimed in claim 3, wherein the material of the metal conductive layer is silver nanowire or carbon nanotube or graphene.

10. The method for integrating the extensible stimulation electrode on the surface of the semi-inflatable micro-balloon as claimed in claim 3, wherein the polyimide substrate layer and the polyimide packaging layer can be replaced by PDMS, Ecoflex or PU adhesive materials.

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